Circuit breakers are automatically operated electrical switches designed to protect electrical circuits from damage caused by overload or short circuit. A basic function is to detect a fault condition and interrupt current flow.
Typically, in a circuit breaker, the electrical contacts are held closed by a latch mechanism having separate first and second engageable members. Initially, the first member may be positioned to contact the second member to restrain and prevent movement of the second member so that the electrical contacts are maintained in a closed position. The latch mechanism may be triggered by moving or pivoting the first member out of engagement with the second member to allow the second member to move and open the electrical contacts.
In addition, often a circuit breaker includes a “quick-make” feature that allows electrical contacts to be closed quickly from the fully open position to the closed position. The speed of the closing of the electrical contacts is independent of how a handle operated by a user is used to effect the closing of the electrical contacts from the open position, i.e., the contact speed is independent of how fast or slow the handle is moved. Traditional over-center toggle mechanisms achieve a change in linkage orientation with respect to spring tension so that at a certain critical point in the handle movement, a balance of forces will cause the quick rotation of linkages to snap the contacts closed.